Mobile telecommunications networks are known in which data is stored such that there is no access control when such data is accessed by network nodes in the mobile communications networks. This method has been sufficiently reliable until now since these networks were intrinsically closed and no external access to the data was thus possible. One example of such a network is a mobile communications network constructed on the basis of the GSM Standard (Global System for Mobile Communication), in which user-specific data is stored, for example, in a home location register (HLR). Other network elements used in these GSM networks can access the home location register without any access control.
In the course of the opening up of mobile communications networks, however, it is no longer possible to assume that a network will be intrinsically closed, since external devices (for example network nodes which provide services for an end user=application server) can also access such data. In mobile communications networks based on the UMTS Standard (UMTS=Universal Mobile Telecommunication Service), it is even possible for a number of network operators to use one network jointly.
A device for checking the authorization for use of protected services, in which algorithms and data which are required for checking authorization are stored in a computer, is known from German Patent Specification DE 195 24 822 C1.
A method for using a mobile telephone to check data stored in a computer is known from German Laid-Open Specification DE 199 41 922 A1, in which an interrogation data record is transmitted from the mobile telephone to an SMS computer, which checks the legitimacy and then calls up information from computers or databanks.